Characteristics of Streptomyces flavogriseus beta-xylosidase and its use in xylan hydrolysis
1999
El-Sawah, M.M.A. | Ashour, E.H. (Mansoura Univ. (Egypt). Dept. of Microbiology) | Shady, T.S.M.
Beta-xylosidase was induced when Streptomyces flavogriseus strain was grown in shake-culture of a animal salt medium containing 1 percent wheat straw hemicellulose for 3 days at 30 degree centigrade. The intracellular beta-xylosidase was separated by precipitation with acetone, ammonium sulphate and purified on Sephadex G-150. The enzyme had an apparent molecular weight of 85 Kda as determined by SDS-gel electrophoresis. Beta-xylosidase showed maximum activity at pH 6.5 and temperature 40 degree centigrade. It was stable at pH 6.0-8.0. Heat treatment to 45 degree centigrade for 1 h did not cause any inhibition for enzyme activity. It was stable for 5 months at 4 degree centigrade. It was also stable against freezing, thawing and lyophilization with 5.65 percent loss per cycle. It hydrolyzed roh-nitrophenyl-beta-D- xylopyranoside readily with a K base m of 1.1 mM. I base 2, and HgCl2 were the most potent inhibitors for beta-xylosidase activity. Xylose was inhibitory towards the enzyme and the inhibition constant was 5.2 mM. The activity of beta-xylosidase and xylanase acting together was greater than the sum of the individual activities, indicating the synergism between St. flavogriseus xylanolytic components in the hydrolysis of insoluble hemicelluloses.
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